The Science · Training load
A useful training score starts a conversation.
JStress describes how much work you reported. Your goal, sport and response explain what to do with it.
The evidence behind the number
Foster and colleagues tested a session rating of perceived exertion approach in human cycling and basketball exercise. Its relationship with a heart-rate method supported its use for quantifying training across those settings, although the absolute scores differed. Foster et al., 2001.
JMM calls completed minutes multiplied by whole-session RPE “JStress,” in arbitrary units. That is a presentation name for session-RPE load. It does not make the method proprietary or prove that a particular JMM training recommendation will improve your performance.
The same score can describe different sessions
Consider two illustrative logs: 60 minutes at RPE 3 and 30 minutes at RPE 6 both give 180 AU. The number alone cannot tell whether you trained endurance, speed, technical skill or strength. It also cannot distinguish the tissue loading of running from cycling.
A coach should preserve the purpose of the session. Record interval pace or power, sets and repetitions, technique, completion, pain and how you felt afterward. Use sport-specific tests to evaluate adaptation; do not make “increase JStress” the training goal.
Trends describe history; they do not diagnose readiness
J Base and J Recent smooth daily session-RPE load using slower 42-day and faster 7-day settings. J Balance is their difference. These settings are model choices. They are not measurements of fitness, fatigue or a personal safe training limit.
Research in recreational runners shows that different ways of calculating load changes can yield different answers. A chart’s formula matters, and one model should not be substituted for another without explanation. Comparison of training-load calculation methods, 2024.
A negative balance calls for context, not an automatic rest day. A positive balance does not clear someone with pain or illness to train. Missing sessions or a short history can distort both. There is no JMM claim that these four metrics predict injury or establish an optimal race-day value.
JMM keeps an unrecorded day unknown, rather than treating it as rest. The trend restarts after a gap: J Recent requires 7 consecutive known days, and J Base and J Balance require 42. These display rules make incomplete history visible; they are not biological cutoffs. The method guide includes the exact formula and rest-day rule.
What a transparent daily coaching explanation looks like
Illustrative wording, not an assessment of your account:
“You reported 45 minutes at effort 4 yesterday: 180 AU. Today’s choice also depends on your symptoms, sleep and the purpose of the next quality session. Two recent sessions have no effort rating, so I cannot describe your full recent load. Please complete those reports before interpreting the trend.”
An AI coach should identify source dates, missing inputs and the reason for an adjustment. Athletes and coaches should be able to correct mistaken inputs. A plan estimate, imported provider score and completed session report must remain distinguishable.
A practical review after each session
- Save actual duration and a consistent whole-session RPE.
- Check whether the intended session purpose was achieved.
- Record unusual pain, symptoms, sleep disruption or environmental conditions.
- Review the trend with these details before changing the next session.
With no device, these reports still give useful information. With a device, they add context that a sensor cannot supply by itself.